Lactic mordant.



UNITED STATES PATENT OFFICE.

LACTIC lVl ORDANT.

Specification of Letters Patent.

Patented Dec. 12, 1905.

Application filed March 6, 1905. Serial'No. 248,645.

citizen of the United States of America, re-

siding at ,Littleton, in the county of Middlesex and State of Massachusetts, have invented certain new and useful Improvements in Mordants, of which the following is'a specification.

This invention relates to that class of mordants which are used as auxiliary agents in dyeing to facilitate, enhance, or modify the action of the principal mordant or of the'dyestuff itself, or of both, and which are therefore technically known as assistant mordants or simply as assistants. Of this class acid potassium tartrate, commonly called tartar, is a well-known example, and the same may likewise be said of lactic acid. These assistant mordants find wide application in association with such principal mordants as potassium bichromate and sodium bichromate, and they are likewise used to some extent when mordanting with other chromium salts or with salts of aluminium or of titanium. They are also frequently useful for the promotion of even or uniform dyeing when added to the dye-bath directly without the presence of other mordants.

When lactic acid is used alone as an assistant mordant, its strong reducing power and penetrating capacity render its action too drastic and rapid for accomplishing even and uniform dyeing; and the object of this invention is to modify and regulate its action in such manner as to enable its valuable properties to be more efficiently and satisfactorily utilized. This is done by mixing it in solution with ammonium acetate or other neutral ammonium salt, such as ammonium sulfate, ammonium oxalate, or ammonium formate. Advantage is thus taken not only of the presence of ammonia in an ionic state within the solution, but also of the tendency of such ammonium salts to decompose slowly upon heating their aqueous solutions and gradually to ive off ammonia to the watervapor even w en an excess of acid is present in the solution. Such a mixture of free or uncombined lactic acid with a neutral ammonium salt constitutes an assistant mordant, which in the mordant-bath or in the dyebath not only promotes and facilitates the efiective action and thorou h penetration of the principal. mordant or t e dyestufi, but also 'at the same time causes and secures the 510W and uniform deposition of the same in and upon the material to be dyed. The proportion of free lactic acid to neutral ammonium salt depends upon the acid, neutral, or basic character of the principal mordant or of the dyestuff with which this assistant mordant is to be used. Under ordinary conditions these components should be mixed in equal molecular proportionsthat is to say, one molecule of free lactic acid, represented by the chemical symbols C H O to one molecule of ammonium salt, represented, for example, in the case of ammonium acetate, by the chemical symbols (N H )C H O or in this particular instance ninety parts by weight, of lactic acid to seventy-seven parts, by weight, of ammonium acetate but in cases where the assistant mordant is intended to be used in association with some strongly-acid principal mordantsuch as chromium fluorid, for instanceit is preferable to compound the assistant mordant with two, three, or even four molecular units of neutral ammonium salt to one molecular unit of free lactic acid, while, on the other hand, with a more neutral principal mordant, such as potassium chromate, it is better that the assistant mordant should be compounded of one molecular unit of neutral. ammonium salt to several molecular units of free lactic acid. The like holds true when the assistant mordant is used alone with one-bath dyestufis. With acid colors it should have its ingredients in the proportion of more than one molecular unit of free lactic acid to one molecular unit of neutral ammonium salt; but with basic dyestuifs the assistant mordant should contain much less than one m0- lecularunit of free lactic acid to one molecular unit of neutral ammonium salt, or, in other words, only such proportion of free lactic acid as will insure its presence in some, but very little, quantity.

In general it may be said that the assistant mordant embodying the present invention consists, essentially, of free lactic acid and neutral ammonium salt in such proportion that the free or uncombined lactic acid will always be present in excess of the acid combined with and required for neutralizing the ammonium of the neutral ammonium salt.

It is to be observed that although in the process of dyeing a mordant-bath may be, and usually is, separate and distinct from a dyestufi-bath, yet when both are required for the attainment of the final result each is, in effect, just as truly a dyeing-bath as is the 2. A dyeing-bath containing in solution as an assistant mordant, free lactic acid and neutral ammonium salt in such proportion that the free lactic acid will be present in excess of the acid which is combined With and is required for neutralizing the ammonium of the neutral ammonium salt.

ALAN A. CLAFLIN.

Witnesses:

REUBEN L. RoBERTs, FLORENCE A. OoLLINs. 

